The present invention relates generally to electrophotography systems, and is applicable particularly, but not exclusively, to electro-printing machines, laser beam printers and copying machines.
Electrophotography systems are currently used in fields of copying art such as electro-copying machines, where an electrostatic latent image is formed on a photosensitive device by projecting thereto an optical image of an original picture and then developed with a desirable toner for formation of a so-called hard copy. An important problem in such a copying technique relates to difficulty being encountered to meet requirements in terms of speed-up of copying, because exposure of the original optical image on the photosensitive device is indispensable to obtaining a copy. Thus, in view of the speed-up, an apparatus additionally having a printing function has been proposed as disclosed in U.S Pat. No. 2576047, where an electrostatic latent image is formed on a photosensitive device (made of zinc oxide) by an exposure of an optical image of an original picture and then toner-developed and fixed to obtain a printing plate whereby printing is effected through processes such as charging, exposure, transferring and fixing. There is a problem which arises with such prior art technique, however, in that the printing plate is required to be replaced with new one in switching from the printing mode to the copying mode, thereby resulting in being troublesome in operation. In addition, such prior art technique is not applicable to laser beam printers which are arrange so as to form an electrostatic latent image in accordance with an information signal corresponding to an image to be recorded. Japanese Patent Provisional Publication No. 59-15249 discloses a system having functions for application to both copying machines and laser beam printers. However, this system is not applicable to printing machines.